110 NATURE AND LIFE. 
The hue of certain flowers even varies according to the 
altitude. Thus the corolla of the Anthyllis vulneraria 
shades down from white to pale red and vivid purple. In 
general, the vegetation of open, well-lighted places is 
richer in color and development than that of regions not 
accessible to the sun. The nelumbium and the bougain- 
villea will not thrive in English greenhouses, though 
heat is abundantly supplied them, but they unfold com- 
pletely under the clear sky of Montpellier. Some flowers 
originally white afterward deepen in color by the direct 
action of light. Thus Cheiranthus cameleo has a flower 
at first whitish, afterward yellow, and, at last, a violet-red. 
The Stylidium fruticosum has petals which are pale yel- 
low at first, and grow pink. The Cnothera tetraptera 
passes through white, pink, and red colors successively. 
The flowers of the Cobewa scandens are green the first day, 
and violet the next. The Hibiscus mutabilis bears a 
flower which opens at morning with a white hue, and 
grows red during the day. The flower-buds of the Aga- 
panthus umbellatus are white when they begin to unclose, 
and afterward take ona blue tint. If, at the moment of 
leaving its spathe, the flower is wrapped in black paper, 
intercepting the light, it remains white, but regains its 
color in the sun. Edmond Becquerel remarked that if a 
slip of red flowering crassida is allowed to bloom ina 
dimly-lighted room, the petals take a tint half yellow, half 
pink, at the base. Exposure to sunlight for some hours 
occasions a red tinge in all the corollas of these little flow- 
ers. If some parts of the plant are protected by a cover- 
ing of blackened paper, the flowers thus hidden keep the 
faint color which they had in the dim light of the room. 
The tints of fruits in the same way develop under the 
healthy action of daylight, and the rule extends to those 
principles of every nature which give taste and odor to the 
different parts of the plant. 
